<meta charset="utf-8">
(#) Incorrect `WakeLock` usage

!!! WARNING: Incorrect `WakeLock` usage
   This is a warning.

Id
:   `Wakelock`
Summary
:   Incorrect `WakeLock` usage
Severity
:   Warning
Category
:   Performance
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   Initial
Affects
:   Kotlin and Java files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/WakelockDetector.kt)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/WakelockDetectorTest.kt)
Copyright Year
:   2012

Failing to release a wakelock properly can keep the Android device in a
high power mode, which reduces battery life. There are several causes of
this, such as releasing the wake lock in `onDestroy()` instead of in
`onPause()`, failing to call `release()` in all possible code paths
after an `acquire()`, and so on.

NOTE: If you are using the lock just to keep the screen on, you should
strongly consider using `FLAG_KEEP_SCREEN_ON` instead. This window flag
will be correctly managed by the platform as the user moves between
applications and doesn't require a special permission. See
https://developer.android.com/reference/android/view/WindowManager.LayoutParams.html#FLAG_KEEP_SCREEN_ON.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/test/pkg/WakelockActivity3.java:13:Warning: The release() call is
not always reached (because of a possible exception in the path
acquire() → randomCall() → exit; use try/finally to ensure release is
always called) [Wakelock]
    lock.release(); // Should be in finally block
         -------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`src/test/pkg/WakelockActivity3.java`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers
package test.pkg;

import android.app.Activity;
import android.os.PowerManager;

public class WakelockActivity3 extends Activity {
    void wrongFlow() {
        PowerManager manager = (PowerManager) getSystemService(POWER_SERVICE);
        PowerManager.WakeLock lock =
                manager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "Test");
        lock.acquire();
        randomCall();
        lock.release(); // Should be in finally block
    }

    static void randomCall() {
        System.out.println("test");
    }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/WakelockDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("Wakelock")
  fun method() {
     acquire(...)
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("Wakelock")
  void method() {
     acquire(...);
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection Wakelock
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="Wakelock" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'Wakelock'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore Wakelock ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

<!-- Markdeep: --><style class="fallback">body{visibility:hidden;white-space:pre;font-family:monospace}</style><script src="markdeep.min.js" charset="utf-8"></script><script src="https://morgan3d.github.io/markdeep/latest/markdeep.min.js" charset="utf-8"></script><script>window.alreadyProcessedMarkdeep||(document.body.style.visibility="visible")</script>